Shelly-Ann Fraser-Pryce stayed on track for an Olympic sprint double on Monday as fellow Jamaican Veronica Campbell-Brown took her first step towards a third consecutive 200m gold.
Fraser-Pryce, who successfully defended her 100m title in London, looked impressive in easing to victory in heat six of the first round of the women's 200m in a time of 22.71sec.
Campbell-Brown timed 22.75sec in heat five as American Sanya Richards-Ross, chasing a 200m-400m double after winning the one-lap sprint 24 hours earlier, topped the qualifying times with 22.48sec.
Three-time 200m world champion Allyson Felix of America, who finished second behind Campbell-Brown over 200m in Athens 2004 and Beijing 2008, ran 22.71sec.
Felix came into the event in superb form, having run a personal best and world leading time of 21.69 at the US Olympic trials, the fastest for 14 years.
Campbell-Brown ended Felix's winning streak at last year's world championships in Daegu, South Korea, last year.
Asked about the possibility of achieving a trio of titles, Campbell-Brown told BBC TV: "It is a great stiuation to be in, I am not going to let pressure overwhelm me or anything, I am just taking it step by step.
"The objective is to get to the final and just run as best I can there."
Carmelita Jeter, pipped to the 100m gold by Fraser-Pryce, also qualified for Tuesday's semi-finals.
Speaking about recovering after the women's 100m, Felix said: "I am doing pretty good. I got some treatment. I am just excited about this race (the women's 200m)."
The first woman to do the 100-200m double was legendary Dutch runner Fanny Blankers-Koen, who performed the feat in London in 1948.